add more suppressions for mipmap fix

BUG=skia:
TBR=
NOTRY=True
NOTREECHECKS=True

Review URL: https://codereview.chromium.org/828633003
diff --git a/expectations/gm/ignored-tests.txt b/expectations/gm/ignored-tests.txt
index 8b98c4e..cd66dcf 100644
--- a/expectations/gm/ignored-tests.txt
+++ b/expectations/gm/ignored-tests.txt
@@ -62,6 +62,9 @@
 filterbitmap_text_10.00pt
 filterindiabox
 fontmgr_iter
+downsamplebitmap_image_high_mandrill_132x132_12x12.astc
+downsamplebitmap_image_high_mandrill_512.png
+downsamplebitmap_text_high_72.00pt_8888.png
 
 # robertphillips - skia:2995
 blurrects